Aftertreatment of leather dyeings



United States Paten 2,908,543 AFTERTREATMENT F LEATHER DYEINGS N0 Drawing. Application June 29, 1956 Serial No. 594,692

15 Claims. (Cl. 8-13) This invention relates to the aftertreatment of leather dyeings and more particularly to a process for aftertreating leather dyeings to improve their wet fastness properties.

The use of reaction products of formaldehyde and dicyandiamide for fixing soluble products on substrata is well known. Moreparticularly, it is known that the wet fastness of dyeing and prints may be increased by aftertreatment with dicyandiamide-formaldehyde reaction products. Since such aftertreatments to improve the wet fastness of .dyein'gs and prints is usually applied from an aqueous medium, it is highly desirable that the aforesaid reaction products be sufficiently soluble in water to achieve the desired results. Many such reaction products have often had undesirable properties with respect to solubility, stability on storage and during treatment, and the like. In some cases, the shade of the treated dyeing or print is affected. In other cases, the wet fastness of the treated dyeings and prints, particularly leather dyeings and prints, have not been improved to the desired extent. Various other difficulties are known to have been encountered.

It has also been proposed to react dicyandiamide with formaldehyde in the presenceof alkaline or acid catalysts and aqueous media. Thus, in US Patent No. 2,741,- 535 there is disclosed the production of a reaction product from about 1.5 to 2.5 moles of formaldehyde and about 0.5 to 1 mole of a water-soluble easily ionizable ammonium salt of an inorganic or lower fatty acid per mole of dicyandiamide, by heating the aforesaid substances in aqueous media at temperatures of about 80 to 100 C. until the desired reaction product is obtained. While this reaction product has many highly desirable properties and applications, it has been found not to yield the desired degree of improvement in wet fastness properties of leather dyeings.

It is an object of this invention-to provide an improved process for improving the wet fastness properties of leather dyeings. Another object of this invention is the provision of an improved process. for improving leather dyeings by aftertreatment with a reaction product of formaldehydeQan ammonium salt of a strong acid and dicyandiamide. Other objects and advantages will appear as the description proceeds.

The attainment of the above objects is made possible by the instant invention which isbased upon the provision of a process comprisingtreating leather dyeings with an acidic aqueous solution of the product of the reaction of about 1 to 3 moles of formaldehyde, 0.5 to 1 mole of an ammonium salt of a strong acid and 1 mole of dicyandiamide in an acidic aqueous solution at a temperature below about 45 C. The process of the instant invention has been found to yeild leather dyeings which are highly improved with respect to their fastness to wet treatments. Such improved results are surprising and unexpected in view of the relatively inferior results obtained by use of theproduct produced by reacting the ice same reactants in the same proportions and inthe same media but at relatively elevated temperatures of about to C. and the relatively greater water solubility of the reaction products employed herein and produced at a temperature below about 45 C.

The reaction products employed in the process of the instant invention, and their manner of production are disclosed and claimed in the copending application of Cofrancesco and Roberts, Serial No. 594,698, entitled Production of Dicyandiamide-Formaldehyde Reaction Products, filed on even date herewith, and no claim is made thereto per se but only to their use for improving the wet fastness properties of leather dyeings. In general, such reaction products are obtained by reacting from about 1 to 3 moles of formaldehyde, 0.5 to 1 mole of an ammonium salt of a strong acid such as ammonium chloride and 1 mole of dicyandiamide in an acidic aqueous solution at a temperature below about 45 C. In its preferred form, the said reaction product is produced by forming an acidic aqueous solution containing about 1 to 3 moles of formaldehyde, 0.5 to 1 mole of an armmoniurn salt of a strong acid such as ammonium chloride and I mole of dicyandiamide, allowing the resulting exothermic reaction to proceed until a maximum temperature is reached between about 70 to 90 C., and then immediately cooling and maintaining the solution at a temperature below about 45 C. until a water-soluble reaction product is obtained. The reaction is preferably carried out in an amount of water only sufiicient to dissolve the three essential reactants, and with the aid of cooling means to maintain a reaction temperature be low about 45 C. since the reaction is exothermic in nature. Salts other than ammonium chloride which may be employed as a reactant include ammonium phosphate, ammonium bromide, ammonium thiocyanate, ammonium sulfate and the like. Theinitial pH of the reaction medium is generally between about 5.0 and 6.8, the pH of the solution at the end of the reaction being about 2.5 to 3.0 but returning upon standing to about 5.0 to 6.8. When carried out with a minimum of water in the reaction medium, solutions are obtained with concentrations as high as 55 to 60% by weight, which solutions may, if desired, be diluted with water to any desired degree. If desired, the reaction product may be separated from the solution, for example by carefully drying under vacuum at low temperatures to prevent deleterious eifects on the solubility and other properties of said reaction product. It is preferred, however, to employ in the instant process the aqueous solution containing the reaction product as directly produced by its process of manufacture, if desired after further dilution with water to a lower concentration, for example about 35% by weight.

The aftertreatment process of the instant invention may vary from about F up to boiling temperatures, although temperatures of about to F. are usually preferred. The process is generally run for about 20 to 40 minutes, it being understood that the temperature and duration of treatment are interrelated and usually vary in inverse order. The process is carried out under acidic conditions, generally at a pH ranging from 5 .0 to 6.8. In general, the treating solution should contain from about 1 to 15%, and preferably about 2 to 10% of the reaction product by weight of the leather, and substantially all of the reaction product in the solution is taken up by the leather during the treatment since the process is substantive in nature. The particular concentration of reaction product in the treating solution will of course depend in any particular instance upon the amount of dye on the fiber, the depth of shade desired, the leatherzliquor ratio and the like.

The leather to be aftertreated in accordance with the process of the instant invention may have been dyed or printed in any desired manner and with any type of dyestutf the wet fastness properties of which are not completely satisfactory. Such dyestuffs are generally of the water-soluble substantive'type. Particularly improved results with respect to wet fastness properties are achieved in the treatment of leather which has been dyed with azo dyestufis. The following general types of dyestuffs are peculiarly amenable to improvement in accordance with the process of the instant invention:

I. Dyes containing sulfonic acid groups, such as the dyes disclosed in US. Patent No. 2,110,394 as exemplified by Ho s HO3S OzN OH Hal in addition to Alizarine Blue SAP (C1. 1054) Brilliant Indocyanine (Pr. 222, 223), Guinea Green (Cl. 666), Phthalocyanine sulfonic acids and the like.

II. Azo dyes which are capable of forming a complex with metals by reason of the presence of an aromatically bound o-hydroxy-carboxy grouping, such as those conin addition to Chrome Yellow A (C.I. 219), Wool Fast Orange GA (Cl. 274), Pluto Orange GA (Pr. 332), Benzo Chrome Brown BA (Pr. 364) and the like.

III. Azo dyes which are capable of forming a complex With metals due to the presence of an o,o-dihydroxy, hydroxy-carboxy, hydroxy-alkoxy, hydroxyamino or equivalent configuration with respect to an azo linkage, as exemplified by SO H OH OH HO; N=

OzN

IV. Azo dyes containing o,o'-configurations as in Class III above, but devoid of solubilizing groups such as sulfonic and carboxylic acid groups and which'are produced on the fiber by the azoic method, as exemplified by H OdEINO:

OCH;

The leather dyeings to be aftertreated in accordance with the process of the instant invention may have been produced by dyeing processes well known in the art, such dyeings usually containing from about 0.5 to 20% of metallized or unmetallized dyestutr' by weight of the leather. Known metallizing procedures, metallizing agents, preferably copper or chromium compounds, and metallizing assistants and the like may be employed in the production of metallized leather dyeings which are particularly amenable to improvement by the instant process. By way of example, chelating agents in amounts of up to about 15% by weight of the metallizing agent have been found particularly efiective. As such chelating agents there may be mentioned hydroxy carboxylic acids such as lactic, citric, tartaric, and salicyclic acids, and other known agents.

Although not absolutely necessary, further improved results are obtained with respect to insolubilization of I IT the said reaction product by following the ti'eaunent of the leather dyeings in accordance with the above defined process of the instant invention by a further treatment with from about 2 to 6% on the weight of the leather of a lower aliphatic carboxylic acid such as formic acid, acetic acid or the like, or a water-soluble metallic salt of a strong inorganic acid. As the metallic salt, an aluminum salt such as the sulfate, chloride, nitrateplfthe like is preferred, but similar salts of copper, cobalt and nickel or the like may be employed for special efliects. The treatment with the lower aliphatic carboxylic acid or the metal salt is preferably accomplished by addition to the bath containing the leather dyeing afters uflicient time has elapsed for the above defined reaction products to act upon the leather dyeing. However, the treatment with the lower aliphatic carboxylic acid or metal salt may be applied subsequently thereto. It will be understood that both the lower aliphatic carboxylic acid and metal salt maybe applied, either separately or simultaneously. This aftertreatment with the lower aliphatic carboxylic acid and/ or metal salt is applied uman-l ans solution and under approximately the same conditions of temperature and duration as the process of the instant invention with respect to treatment with the above defined reaction products Following treatment of the leather dyeings in accordance with the instant process, including, if desired, aftertreatment with the above-defined lower aliphatic carboxylic acid or metal salt, the treated dyeing need only be washed and dried in air at temperature rangingfrom room-temperature to about 150'F., althoughit will be understood that any suitable drying method. maybe employed. It will also be understood that the aqueous solutions of reaction products employed in the process of the instant invention may, if desired, contain other assistants such as metallizing agents (copper compounds and the like), chelating agents, bufiering agents, wetting agents, and the like.

The following examples in which parts are by weight and proportions based on the weight of the leather unless otherwise indicated are illustrative of the instant invention and are not to'be regarded as limitative:

Example 1 Approximately 100 g. suede sheepskin garment leather is wet back in sufiicient water to cover the skin at 125 F., and containing 2% ammonium hydroxide and 1% Igepal CA 630 (General Aniline & Film Corporation, nonionic alkyl phenoxy polyoxyethylene ethanol wetting agent). The leather is rinsed and refloated at 150 F.

To the bath is added 5% Fastusol Brilliant Blue LSGU, which is (dianisidine: Chicago SS acid) demethylated and coppered. Dyeing is continued for 30 minutes, after which 3% formic acid is added to exhaust the dyestuif.

7% Tanolin R (a commercial basic chromium sulfate) is boiled in twice its weight of water. 10% lactic acid (based on the Tanolin R) is added and the solution reboiled and added to the dyebath which is run at 150 F. for another 30 minutes.

The reaction product of Example 2 of said copending application is diluted with water to produce a 35% solution (concentration of reaction product) and 20% of this solution (by weight of the leather) is added to the dyebath which has a pH of about 5.5. After 30 minutes, 4% aluminum sulfate is added and treatment continued for 30 minutes at 150 F. The dyeing is then dried.

To test for wash-fastness, a piece of multifibered fabric is attached to the above dyeing and the skin washed in a Launder-O-Meter for 30 minutes at 120 F. in a /2% soap solution. After rinsing, the skin is acidified in /2% acetic acid solution and dried.

Fading of the leather dyeing and staining of the multifibered fabric is very slight, indicating a high degree of wash-fastness.

When the above procedure is repeated, but using a,

Similar reaction p oduct o icya id am de fo mal h e and ammonium chloride-reacted atabout (3., there. is considerable fading of the treated leather and staining of the mnltifibered fabric, suliicient to'render. the treated leather dyeing unacceptable.

Example Example 1 is repeated but employing instead of the Tanolin R, 3% copper sulfate,and instead-of the final aluminum sulfate treatment, 3% formic acid. A dyeing isobtained which has excellentwash fastness.

. I "Exam e 3 Example 1 s repeated using the following dyes:

Dye Identity 1. Fastusol Orange L3RA Pr, 73 2. Fa'stosol Orange L7G-. Fr. 72 3. Fastusol Brown 3RA Pr. 4. Fastusol Brown LBRSA Fr. 47 r 5. Fastusol Yellow LRTP. 0.1. 814 6. Fastusol Yellow LRRA. 0.1. 814 7. Fastusol Brown LGA Pr. 28 8. Fastusol Red SBA- Pr. 246 9. Fastusol Red 4BA-. (3.1, 278 10. Fastusol Blue L7GA Pr. 432 11. Fastusol Blue LR Pr. 443 12. Fastusol Blue LFBGL Pr. 443 13. Fastusol Green BA Pr. 425 14. Fastusol TurguoiseBlue LGA. Pr. 278 15. Chrome Yellow Am, C 1.219 16. Wool Fast Orange GA (3.1. 274 17. Pluto Orange GA Pr. 3 3 2 18. Benzo Chrome Brown BA Pr. 364 19. Chrome Fast Yellow RDA 0.1.441

In all cases a relatively high degree of Wash-fastness is obtained which is better than when a reaction product is employed made in similar manner but at a temperature of about 85 C. and which is strikingly better than when no wash-fastness improving agent is used.

This invention has been disclosed with respect to certain preferred embodiments, and various modifications and variations thereof will become obvious to the person skilled in the art. It is to be understood that such modifications and variations are to be included within the spirit and purview of this application and the scope of the appended claims.

I claim:

1. A process for improving the fastness to wet treatments of leather dyeings comprising treating such dyeings with an acidic aqueous solution, substantially devoid of copper compounds, of the product of the reaction of about 1 to 3 moles of formaldehyde, 0.5 to 1 mole of an ammonium salt of a strong acid and 1 mole of dicyandiamide in an acidic aqueous solution, said reaction having been carried out at a temperature below about 45 C.

2. A process as defined in claim 1 wherein said leather dyeing contains an azo dyestufi.

3. A process as defined in claim 2 wherein said azo dyestulf contains metal in complex union in the o,o-positions relative to an azo linkage.

4. A process as defined in claim 2 wherein said azo dyestuff contains an aromatically bound o-hydroxy-carboxy configuration.

5. A process as defined in claim 1 wherein said ammonium salt is ammonium chloride.

6. A process as defined in claim 1 followed by the step of applying to the treated leather dyeings an aqueous solution containing a member of the group consisting of unsubstituted lower aliphatic carboxylic acids and water-soluble metal salts of strong inorganic acids.

7. A process for improving the fastness to wet treatments of leather dyeings comprising treating such dyeings with an acidic aqueous solution, substantially devoid of copper compounds, obtained by forming an acidic aqueous solution containing from about 1 to 3 moles of formaldehyde, 0.5 to 1 mole of an ammonium salt of 7 a strong acid and 1 mole of dicyandiamide, allowing the resulting exothermic reaction to proceed until a maximum temperature is reached betweenabout 70 to 90 C., and then immediately cooling and maintaining the solution at a temperature below about 45 C. until a water-soluble reaction product is obtained.

8. A process as defined in claim 7 wherein said ammonium salt is ammonium chloride.

9. A process as defined in claim 7 followed by the step of applying to the treated leather dyeings an aqueous solution containing a member of the group consisting of unsubstituted lower aliphatic carboxylic acids and water-soluble metal salts of strong inorganic acids.

10. A process as defined in claim 7 wherein said leather dyeing contains an azo dyestufi.

11. A process as defined in claim wherein said azo dyestuif contains metal in complex union in the o,o'-positions relative to an azo linkage.

12. A process as defined in claim 10 wherein said azo dyestutf contains an aromatically bound o-hydroxy-carboxy configuration.

13. A process for improving the fastness to wet treatments of leather dyed with dyes containing metal in complex union in o,o'-positions relative to an azo link age comprising treating such dyeings with an acidic aqueous solution, substantially devoid of copper compounds, of the product of the reaction of about 1 to 3 moles of formaldehyde,-0.5 to 1 mole of ammonium chloride and 1 mole'of dicyandiamide in an acidic aqueous solution, said reaction having been carried out at a temperaturerbelow about 45 C., and then subjecting the treated leather dyeings to the action of an aqueous Solution containing a member of the group consisting of comprising treating such dyeings with an acidic aqueous solution, substantially devoid of copper compounds, of the product of the reaction of about 1 to 3 moles of formaldehyde 0.5. to 1 mole of ammonium chloride and 1 mole of dicyandiamide in. an acidic aqueous solution, said reaction having been carried out at a temperature below about C., and then subjecting the treated leather dyeings to the action of an aqueous solution containing formic acid.

15. A process for improving the fastness to wet treatments of leather dyed with dyes containing metal in complex union in o,o'-positions relative to an azo linkage comprising treating such dyeings with an acidic aqueous solution, substantially devoid of copper compounds, of the product of the reaction of about 1 to 3 moles of forrnaldehyde, 0.5 to 1 mole of ammonium chloride and 1 mole of dicyandiamide in an acidic aqueous solution, said reaction having been carried out at a temperature below about 45 C., and then subjecting the treated leather dyeings to the action of an aqueous solution containing aluminum sulfate.

References Cited in the file of this patent UNITED STATES PATENTS 2,317,965 Bestian Apr. 27, 1943 2,736,749 Robinson Feb. 28, 1956 2,768,055 Streck Oct. 23, 1956 

1. A PROCESS FOR IMPROVING THE FASTNESS TO WET TREATMENTS OF LEATHER DYEINGS COMPRISING TREATING SUCH DYE INGS WITH AN ACIDIC AQUEOUS SOLUTION, SUBSTANTIALLY DEVOID OF COPER COMPOUNDS, OF THE PRODUCT OF THE REACTION OF ABOUT 1 TO 3 MOLES OF FORMALDEHYDE, 0.5 TO 1 MOLE OF AN AMMONIUM SALT OF A STRONG ACID AND 1 MOLE OF DICYANDIAMIDE IN AN ACIDIC AQUEOUS SOLUTION, SAID REACTION HAVING BEEN CARRIED OUT AT A TEMPERATURE BELOW ABOUT 45* C. 